Heating system



AW 0 l e HEATING SYSTEM Original Filed Jan. 29, l

INVENTOR E 407) Mh arrn on WITNESSES:

Patented Aug. 29, 1933 UNITED STATES PATENT OFFICE HEATING SYSTEM Original application January 29, 1931, Serial No.

512,038, now Patent No.

1,835,647, dated December 8, 1931. Divided and this application November 21, 1931. Serial No. 576,459

2 Claims.

This application is a division of my application. Serial No. 512,036, filed January 29, 1931, and which issued as Patent 1,835,647, Dec. 8, 1931.

My invention relates to rectifier systems and 5 particularly to improved means for controlling the rectifier output.

An object of my invention is to provide a rectifier system in which a switching element is located in the rectifier tube itself for starting and stopping the direct current flow in the rectifier output.

A further objectof my invention is to provide means for stopping the flow of direct current in a rectifier output in response to the opening or closing of delicate contacts.

A still further object of my invention is to provide means for controlling the amount of current supplied to a thermostat controlled heater or the like without causing destructive sparking at the thermostat contacts.

In accordance with my invention, thermostat contacts control the amount of current supplied to a tuning-fork heater by opening or closing a circuit which applies a negative potential to control grids located in two three-electrode rectifier tubes. When the grids are negative, the rectifier tubes are so blocked that no plate current fiows to the heater.

Other features and advantages of my invention will appear from the following description, taken in connection with the accompanying drawing, in which:

Figure 1 is a diagrammatic view of the apparatus and electrical connections employed in practicing my invention, and

Fig. 2 comprises a view partly in section and partly in elevation of the tuning fork holder shown in Fig. 1.

Referring to the drawing, the apparatus comprises a tuning-fork holder supported in a heater box 11 by means of supporting columns 12. The heater box 11 is enclosed by another heater box 13 for preventing too great variations in the temperature of the surrounding atmosphere. The r temperature of the air between the boxes 11, and

13 is kept approximately constant by means of a heater winding 14 connected in series with a bimetallic thermostat 15.

The tuning-fork holder 10 is of the same construction as that described in Patent No. 1,743,178, issued to Lester J. Wolf, January 14, 1930 and assigned to the Westinghouse Electric Manufacturing Company. It comprises two solid metallic blocks 16 and 17, preferably of brass, the blocks having holes 18 and 19, respectively, drilled off 55 center therein. The blocks have larger threaded holes drilled at right angles to the holes 18 and 19 and communicating with them in which electromagnet driving units 20 and 21 are supported. The blocks 16 and 17 are clamped together by means of bolts 22, with their thin walls adjacent to each other and with a sheet 23 of magnetic material between them. In this way, two wall portions are formed which are separated by a thin partition of magnetic material and nonmagnetic material. A square notch 24 is cut in the middle upper edge of the partition.

The tuning fork 25 is clamped, by means of bolts 26, between two solid metal blocks 27 and 28, preferably of brass. These blocks are secured, by bolts 29, to the blocks 16 and 17 in such positions that a. portion of the tuning fork 25 is located within the notch 24 cut in the partition, while the prongs 30 and 31 are located within the holes 18 and 19.

The tuning-fork driving elements comprise telephone-receiver units 20 and 21 having pole pieces 32 adjacent to the prongs 30 and 31 of the tuned fork. The pole pieces 32 are softiron members attached to 'the poles of a permanent magnet 33. They have coils 34 and 34' mounted 0 thereon which are connected to the binding posts 35 and 35, respectively.

A thermostat 37 is held in intimate contact with one of the blocks of-the tuning-fork holder 10. In the example illustrated, this is done by placing the thermostat in a hole through the brass block 28. The mercury thermostat 37, which may be of any well known construction, is fastened in a brass tube 38 by means of a heatconducting wax 39. The external diameter of the tube 38 is such that it will fit snugly into the hole.

The thermostat 37 is provided with two contact points 40 and 41 which so extend into the glass tube of the thermostat that, when the tuning fork holder 10 is heated sufficiently, the mercury will electrically connect the two contact points.

The tuning-fork holder is heated by means of two heater coils 42 and 43 which are preferably spaced away from the fork holder. The heater coils are supplied with heating current from a double-wave rectifier which comprises two threeelectrode vacuum tubes 44 and 45.

The filaments 46 of the vacuum tubes are heated by alternating current supplied from the secondary 47 of a transformer 48. The plates 49 are connected to opposite ends of a high-voltage secondary winding 50. The heater windings 42 and 43 are connected to the rectifier through a conductor 51 which is connected to the mid-point of the plate secondary winding 50 and through a conductor 52 which is connected to the mid-point of the filament winding 47.

When the thermostat contacts 40 and 41 are electrically connected, a biasing battery 53 is connected to grids 54 through conductor 55, the thermostat contacts 40 and 41, conductor 56 and a resistor 57. The grids 54 are preferably connected to ground through a high-resistance grid leak 58 which is shunted by a condenser 59, the condenser 59 being for the purpose of reducing inductive kick in the system.

In operation, the rectifier supplies current to the heater coils 42 and 43 so long as the metallic blocks comprising the fork holder 10 are below a predetermined temperature. As soon as this temperature is exceeded, the mercury column in the thermostat 37 rises to connect the negative terminal of the biasing battery 53 to the grids 54 of the rectifier tubes. The tubes are blocked immediately, and the fiow of current through the heater windings 42 and 43 ceases. As soon as the temperature of the metallic blocks falls below a predetermined value, the biasing battery 53 is disconnected from the grids 54, and current again fiows through the heater windings.

Various modifications may be made in my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and are set forth in the appended claims.

I claim as my invention:

1. Electrical apparatus comprising a housing,

a unit within said housing to be heated, a heater element for said unit, a thermostat responsive to temperature changes in said unit, said thermostat having contact points, a rectifier of the high-vacuum type having a control element therein, said heater element being supplied with current from the output of said rectifier, means responsive to the closing of said contact points for changing the potential on said control element, 9. second housing substantially enclosing said first-mentioned housing in spaced relationship thereto and controlled heating means for regulating the temperature of the space between said housings.

2. Electrical apparatus comprising a housing, a unit within said housing to be heated, a heater for supplying heat to said unit, a thermostat responsive to temperature changes in said unit, said thermostat having contact points, a doublewave rectifier oi the vacuum tube type comprising twoanodes and a control electrode for each of said anodes, said heater being supplied with current from said rectifier, means, including said thermostat contact points, for applying a nega- RALPH N. HARMON. 

